Effects of temafloxacin and ciprofloxacin on the pharmacokinetics of caffeine

Highly sensitive and selective electrochemical sensor for simultaneous determination of gallic acid, theophylline and caffeine using poly(l-proline) decorated carbon nanotubes in biological and food samples

In this work, a novel, simple and reproducible poly(l-proline)/functionalized multi-walled carbon nanotube composite on glassy carbon electrode (poly(PRO)-MWCNTs/GCE) was developed as an electrochemical sensor for the simultaneous determination of gallic acid (GA), theophylline (TP) and caffeine (CAF) by differential pulse voltammetry (DPV). The sensing platform was optimized by experimental design and response surface methodology, using various factors affecting polymerization and detection, such as electropolymerization time and potential, and pH, respectively. As a result, the dispersion conditions were the mixing of 1.78 mg MWCNTs with 1.00 mL l-proline solution to 4.14 mg mL-1 (in SDBS 0.5%), followed by 21 min of sonication with electropolymerization by 16 cyclic scans. In addition, the final analysis was performed at a pH of 3.00 and prior accumulation at 0.350 V for 40 s. The electrochemical behavior of GA, TP and CAF on the optimized sensor was investigated. As a result, the electrode preserves and synergistically combines the properties of each modifier. This new electrochemical sensor showed superior electrocatalytic properties for the oxidation of GA, TP and CAF, which significantly improved the sensitivity of the three compounds. Under the optimized experimental conditions, the detection limits achieved by S/N were 0.03, 0.04 and 0.11 μmol L-1 for GA, TP and CAF, respectively. The analysis of real samples was successfully performed in human breast milk, tea, infusion of yerba mate, coffee, Coca-Cola zero and energy drink, showing good recoveries, ranged between 87 and 108%. The proposed sensor also showed good selectivity, repeatability and reproducibility, indicating feasibility and reliability. This is the first time that the l-proline monomer is used as a dispersant for MWCNTs and as a precursor for the in-situ polymerization of the proline polymer. Previously, the electropolymerizations were carried out with the monomer in solution rather than as an exfoliant of MWCNTs, where the polymer is electrosynthesized between MWCNTs rather than on them. In this way, the large specific surface area and strong adsorption ability of the nanomaterial are enhanced, and the ability to promote electron transfer reaction is increased, which provides enough effective reaction sites.

Caffeine, Paraxanthine, Theophylline, and Theobromine Content in Human Milk

This study aimed to assess the content of caffeine and its metabolites—paraxanthine, theophylline, and theobromine—in breast milk according to selected factors. Samples of human milk were collected from 100 women living in the east–northeast region of Poland. Information on the consumption of beverages and foods containing caffeine was collected using a 3 day food record. The determination of caffeine and its metabolite content was performed using liquid chromatography–mass spectrometry (LC–MS/MS). This study research showed that more caffeine was found in the milk of women living in cities, with secondary education, aged 34–43, and also in milk from the 3rd and 4th lactation periods (p ≤ 0.05). Factors such as place of residence, level of education, age, and stage of lactation influenced the nutritional choices of breastfeeding women, which had an impact on the level of caffeine and its metabolites in breast milk. A positive correlation was found between the consumption of caffeine with food and drinks and its level in human milk.

Prediction of drug-drug interactions using physiologically-based pharmacokinetic models of CYP450 modulators included in Simcyp software

In recent years, physiologically based PharmacoKinetic (PBPK) modeling has received growing interest as a useful tool for the assessment of drug pharmacokinetics. It has been demonstrated to be informative and helpful to quantify the modification in drug exposure due to specific physio-pathological conditions, age, genetic polymorphisms, ethnicity and particularly drug-drug interactions (DDIs). In this paper, the prediction success of DDIs involving various cytochrome P450 isoenzyme (CYP) modulators namely ketoconazole (a competitive inhibitor of CYP3A), itraconazole (a competitive inhibitor of CYP3A), clarithromycin (a mechanism-based inhibitor of CYP3A), quinidine (a competitive inhibitor of CYP2D6), paroxetine (a mechanism-based inhibitor of CYP2D6), ciprofloxacin (a competitive inhibitor of CYP1A2), fluconazole (a competitive inhibitor of CYP2C9/2C19) and rifampicin (an inducer of CYP3A) were assessed using Simcyp^® software. The aim of this report was to establish confidence in each CYP-specific modulator file so they can be used in the future for the prediction of DDIs involving new victim compounds. Our evaluation of these PBPK models suggested that they can be successfully used to evaluate DDIs in untested scenarios. The only noticeable exception concerned a quinidine inhibitor model that requires further improvement. Additionally, other important aspects such as model validation criteria were discussed.

Ciprofloxacin blocked enterohepatic circulation of diclofenac and alleviated NSAID-induced enteropathy in rats partly by inhibiting intestinal β-glucuronidase activity

AIM

Diclofenac is a non-steroidal anti-inflammatory drug (NSAID), which may cause serious intestinal adverse reactions (enteropathy). In this study we investigated whether co-administration of ciprofloxacin affected the pharmacokinetics of diclofenac and diclofenac-induced enteropathy in rats.

METHODS

The pharmacokinetics of diclofenac was assessed in rats after receiving diclofenac (10 mg/kg, ig, or 5 mg/kg, iv), with or without ciprofloxacin (20 mg/kg, ig) co-administered. After receiving 6 oral doses or 15 intravenous doses of diclofenac, the rats were sacrificed, and small intestine was removed to examine diclofenac-induced enteropathy. β-Glucuronidase activity in intestinal content, bovine liver and E coli was evaluated.

RESULTS

Following oral or intravenous administration, the pharmacokinetic profile of diclofenac displayed typical enterohepatic circulation, and co-administration of ciprofloxacin abolished the enterohepatic circulation, resulted in significant reduction in the plasma content of diclofenac. In control rats, β-glucuronidase activity in small intestinal content was region-dependent: proximal intestine<distal intestine<ileal valve. Administration of ciprofloxac caused significant reduction of β-glucuronidase activity in distal small intestine, and particularly in ileal valve. Furthermore, ciprofloxacin (10-2000 μmol/L) dose-dependently inhibited β-glucuronidase activity in distal small intestine content or E coli incubated in vitro, but did not affect that in proximal small intestine content or bovine liver incubated in vitro. After receiving 6 oral doses or 15 intravenous doses of diclofenac, typical enteropathy was developed with severe enteropathy occurred in distal small intestine. Co-administration of ciprofloxacin significantly alleviated diclofenac-induced enteropathy.

CONCLUSION

Co-administration of ciprofloxacin attenuated enterohepatic circulation of diclofenac and alleviated diclofenac-induced enteropathy in rats, partly via the inhibition of intestinal β-glucuronidase activity.

Application of a Physiologically Based Pharmacokinetic Model to Study Theophylline Metabolism and Its Interactions With Ciprofloxacin and Caffeine

Theophylline is a commonly used bronchodilator. However, due to its narrow therapeutic range, moderate elevation of serum concentration can result in adverse drug reactions (ADRs). ADRs occur because of interhuman pharmacokinetic variability and interactions with coprescribed medicines. We developed a physiologically based pharmacokinetic (PBPK) model of theophylline, caffeine, and ciprofloxacin metabolisms to: examine theophylline pharmacokinetic variability, and predict population‐level outcomes of drug–drug interactions (DDIs). A simulation‐based equation for personalized dosing of theophylline was derived. Simulations of DDI show that calculated personalized doses are safe even after cotreatment with large doses of strong inhibitors. Simulations of adult populations indicate that the elderly are most susceptible to ADRs stemming from theophylline–ciprofloxacin and theophylline–caffeine interactions. Females, especially Asians, due to their smaller average size, are more susceptible to DDI‐induced ADRs following typical dosing practices. Our simulations also show that the higher adipose and lower muscle fractions in females significantly alter the pharmacokinetics of theophylline or ciprofloxacin.

Pharmacokinetic drug interactions of antimicrobial drugs: a systematic review on oxazolidinones, rifamycines, macrolides, fluoroquinolones, and Beta-lactams

Like any other drug, antimicrobial drugs are prone to pharmacokinetic drug interactions. These drug interactions are a major concern in clinical practice as they may have an effect on efficacy and toxicity. This article provides an overview of all published pharmacokinetic studies on drug interactions of the commonly prescribed antimicrobial drugs oxazolidinones, rifamycines, macrolides, fluoroquinolones, and beta-lactams, focusing on systematic research. We describe drug-food and drug-drug interaction studies in humans, affecting antimicrobial drugs as well as concomitantly administered drugs. Since knowledge about mechanisms is of paramount importance for adequate management of drug interactions, the most plausible underlying mechanism of the drug interaction is provided when available. This overview can be used in daily practice to support the management of pharmacokinetic drug interactions of antimicrobial drugs.

A quantitative framework and strategies for management and evaluation of metabolic drug-drug interactions in oncology drug development: new molecular entities as object drugs

This article outlines general strategies for the management and evaluation of pharmacokinetic drug-drug interactions (DDIs) resulting from perturbation of clearance of investigational anticancer drug candidates by concomitantly administered agents in a drug development setting, with a focus on drug candidates that cannot be evaluated in first-in-human studies in healthy subjects. A risk level classification is proposed, based on quantitative integration of knowledge derived from preclinical drug-metabolism studies evaluating the projected percentage contribution [f(i)(%)] of individual molecular determinants (e.g. cytochrome P450 isoenzymes) to the overall human clearance of the investigational agent. The following classification is proposed with respect to susceptibility to DDIs with metabolic inhibitors: a projected maximum DDI expected to result in a ≤1.33-fold increase in exposure, representing a low level of risk; a projected maximum DDI expected to result in a >1.33-fold but <2-fold increase in exposure, representing a moderate level of risk; and a projected maximum DDI expected to result in a ≥2-fold increase in exposure, representing a potentially high level of risk. For DDIs with metabolic inducers, the following operational classification is proposed, based on the sum of the percentage contributions of enzymes that are inducible via a common mechanism to the overall clearance of the investigational drug: <<25%, representing a low level of risk; <50%, representing a moderate level of risk; and ≥50%, representing a potentially high level of risk. To ensure patient safety and to minimize bias in determination of the recommended phase II dose (RP2D), it is recommended that strong and moderate inhibitors and inducers of the major contributing enzyme are excluded in phase I dose-escalation studies of high-risk compounds, whereas exclusion of strong inhibitors and inducers of the contributing enzyme(s) is recommended as being sufficient for moderate-risk compounds. For drugs that will be investigated in diseases such as glioblastoma, where there may be relatively frequent use of enzyme-inducing antiepileptic agents (EIAEDs), a separate dose-escalation study in this subpopulation is recommended to define the RP2D. For compounds in the high-risk category, if genetic deficiencies in the activity of the major drug-metabolizing enzyme are known, it is recommended that poor metabolizers be studied separately to define the RP2D for this subpopulation. Whereas concomitant medication exclusion criteria that are utilized in the phase I dose-escalation studies will probably also need to be maintained for high-risk compounds in phase II studies unless the results of a clinical DDI study indicate the absence of a clinically relevant interaction, these exclusion criteria can potentially be relaxed beyond phase I for moderate-risk compounds, if supported by the nature of clinical toxicities and the understanding of the therapeutic index in phase I. Adequately designed clinical DDI studies will not only inform potential relaxation of concomitant medication exclusion criteria in later-phase studies but, importantly, will also inform the development of pharmacokinetically derived dose-modification guidelines for use in clinical practice when coupled with adequate safety monitoring, as illustrated in the prescribing guidance for many recently approved oncology therapeutics.

Ciprofloxacin-induced theophylline toxicity: a population-based study

PURPOSE

Ciprofloxacin can inhibit the cytochrome P450-mediated metabolism of theophylline, but the clinical relevance of this drug interaction is uncertain. We studied the risk of theophylline toxicity associated with the co-prescription of ciprofloxacin and theophylline.

METHODS

This was a population-based, nested case-control study of a cohort of Ontario residents aged 66 years of age or older treated with theophylline between April 1, 1992 and March 31, 2009. Within this group, case patients were those hospitalized with theophylline toxicity. For each case, 50 age- and sex-matched control patients were identified from the same cohort. The odds ratio (OR) for the association between hospitalization for theophylline toxicity and receipt of ciprofloxacin in the 14 days preceding hospitalization was determined.

RESULTS

Among the 77,251 elderly patients receiving therapy with theophylline, 180 eligible case patients hospitalized for theophylline toxicity and 9000 matched controls were identified. Following multivariable adjustment, a nearly twofold increase in the risk of theophylline toxicity following the receipt of ciprofloxacin was observed [adjusted OR 1.86, 95% confidence interval (CI) 1.18-2.93]. In contrast, there was no increased risk of theophylline toxicity within a group of patients receiving neutral comparator antibiotics (levofloxacin, trimethoprim-sulfamethoxazole or cefuroxime) (adjusted OR 0.78; 95% CI 0.38-1.62).

CONCLUSION

Treatment with ciprofloxacin is associated with a significant increase in the risk of theophylline toxicity. When clinically appropriate, alternate antibiotics should be considered for elderly patients receiving theophylline.

Clinically significant pharmacokinetic interactions between dietary caffeine and medications

Caffeine from dietary sources (mainly coffee, tea and soft drinks) is the most frequently and widely consumed CNS stimulant in the world today. Because of its enormous popularity, the consumption of caffeine is generally thought to be safe and long term caffeine intake may be disregarded as a medical problem. However, it is clear that this compound has many of the features usually associated with a drug of abuse. Furthermore, physicians should be aware of the possible contribution of dietary caffeine to the presenting signs and symptoms of patients. The toxic effects of caffeine are extensions of their pharmacological effects. The most serious caffeine-related CNS effects include seizures and delirium. Other symptoms affecting the cardiovascular system range from moderate increases in heart rate to more severe cardiac arrhythmia. Although tolerance develops to many of the pharmacological effects of caffeine, tolerance may be overwhelmed by the nonlinear accumulation of caffeine when its metabolism becomes saturated. This might occur with high levels of consumption or as the result of a pharmacokinetic interaction between caffeine and over-the-counter or prescription medications. The polycyclic aromatic hydrocarbon-inducible cytochrome P450 (CYP) 1A2 participates in the metabolism of caffeine as well as of a number of clinically important drugs. A number of drugs, including certain selective serotonin reuptake inhibitors (particularly fluvoxamine), antiarrhythmics (mexiletine), antipsychotics (clozapine), psoralens, idrocilamide and phenylpropanolamine, bronchodilators (furafylline and theophylline) and quinolones (enoxacin), have been reported to be potent inhibitors of this isoenzyme. This has important clinical implications, since drugs that are metabolised by, or bind to, the same CYP enzyme have a high potential for pharmacokinetic interactions due to inhibition of drug metabolism. Thus, pharmacokinetic interactions at the CYP1A2 enzyme level may cause toxic effects during concomitant administration of caffeine and certain drugs used for cardiovascular, CNS (an excessive dietary intake of caffeine has also been observed in psychiatric patients), gastrointestinal, infectious, respiratory and skin disorders. Unless a lack of interaction has already been demonstrated for the potentially interacting drug, dietary caffeine intake should be considered when planning, or assessing response to, drug therapy. Some of the reported interactions of caffeine, irrespective of clinical relevance, might inadvertently cause athletes to exceed the urinary caffeine concentration limit set by sports authorities at 12 mg/L. Finally, caffeine is a useful and reliable probe drug for the assessment of CYP1A2 activity, which is of considerable interest for metabolic studies in human populations.

Absence of effect of rufloxacin on theophylline pharmacokinetics in steady state

Several quinolone antibacterial agents are known to inhibit the metabolism of theophylline, with the potential to cause adverse events due to raised theophylline concentrations during coadministration. A randomized crossover study was therefore conducted with 12 healthy male volunteers (ages, 23 to 34 years; body weight, 64 to 101 kg) to evaluate a possible interaction between rufloxacin and theophylline. Both drugs were administered at steady state. Following the administration of an oral loading dose of 400 mg on day 1, rufloxacin was given orally at 200 mg once daily on days 2 to 7 during one period only. During both periods, 146 mg of theophylline was administered orally twice daily for 3 days (which were days 4 to 6 of the rufloxacin coadministration period) and intravenously once the next morning to test for an interaction. Theophylline and rufloxacin concentrations were measured by reversed-phase high-pressure liquid chromatography, the pharmacokinetics of theophylline at steady state following administration of the last dose were calculated by compartment-model-independent methods. To compare the treatments, analysis of variance-based point estimates and 90% confidence intervals (given in parentheses) were calculated for the mean ratios of the pharmacokinetic parameters from the test (rufloxacin coadministration) over those from the reference (theophylline without rufloxacin) period. These were as follows: maximum concentration at steady state, 1.01 (0.96 to 1.07); area under the concentration-time curve from 0 to 12 h, 0.98 (0.94 to 1.02); half-life, 0.99 (0.95 to 1.03); total clearance at steady state, 1. 02 (0.99 to 1.06); and volume of distribution in the elimination phase, 1.01 (0.97 to 1.05). In conclusion, rufloxacin did not affect theophylline pharmacokinetics at steady state. Therefore, therapeutic coadministration of rufloxacin and theophylline is not expected to cause an increased incidence of theophylline-related adverse events.

Ciprofloxacin. An updated review of its pharmacology, therapeutic efficacy and tolerability

Ciprofloxacin is a broad spectrum fluoroquinolone antibacterial agent. Since its introduction in the 1980s, most Gram-negative bacteria have remained highly susceptible to this agent in vitro; Gram-positive bacteria are generally susceptible or moderately susceptible. Ciprofloxacin attains therapeutic concentrations in most tissues and body fluids. The results of clinical trials with ciprofloxacin have confirmed its clinical efficacy and low potential for adverse effects. Ciprofloxacin is effective in the treatment of a wide variety of infections, particularly those caused by Gram-negative pathogens. These include complicated urinary tract infections, sexually transmitted diseases (gonorrhoea and chancroid), skin and bone infections, gastrointestinal infections caused by multiresistant organisms, lower respiratory tract infections (including those in patients with cystic fibrosis), febrile neutropenia (combined with an agent which possesses good activity against Gram-positive bacteria), intra-abdominal infections (combined with an antianaerobic agent) and malignant external otitis. Ciprofloxacin should not be considered a first-line empirical therapy for respiratory tract infections if penicillin-susceptible Streptococcus pneumoniae is the primary pathogen; however, it is an appropriate treatment option in patients with mixed infections (where S. pneumoniae may or may not be present) or in patients with predisposing factors for Gram-negative infections. Clinically important drug interactions involving ciprofloxacin are well documented and avoidable with conscientious prescribing. Recommended dosage adjustments in patients with impaired renal function vary between countries; major adjustments are not required until the estimated creatinine clearance is < 30 ml/min/1.73m2 (or when the serum creatinine level is > or = 2 mg/dl). Ciprofloxacin is one of the few broad spectrum antibacterials available in both intravenous and oral formulations. In this respect, it offers the potential for cost savings with sequential intravenous and oral therapy in appropriately selected patients and may allow early discharge from hospital in some instances. In conclusion, ciprofloxacin has retained its excellent activity against most Gram-negative bacteria, and fulfilled its potential as an important antibacterial drug in the treatment of a wide range of infections. Rational prescribing will help to ensure the continued clinical usefulness of this valuable antimicrobial drug.

Health risks of herbal remedies

Herbal remedies can result in indirect health risks when they delay or replace a more effective form of conventional treatment or when they compromise the efficacy of conventional medicines. Herbal remedies can also be associated with direct health risks. Long-standing traditional experience may tell much about striking and predictable symptoms of acute toxicity but it is a less reliable tool for the detection of reactions which are inconspicuous, develop gradually or have a prolonged latency period, or which occur uncommonly. Another reason why safety claims cannot always be based on traditional empiricism is that not all herbal remedies are firmly rooted in traditional medicine. The risk of a herbal remedy producing an adverse reaction depends not only on the remedy and its dosage but also on consumer-related parameters, such as age, genetics, concomitant diseases and concurrent use of other drugs. Another important determinant of the toxicity of herbal remedies is their quality. What is already known about the risks of herbal remedies must be systematically collected, disseminated and acted upon. What is yet unknown must be found out by herbal postmarketing surveillance and experimental research.

Caffeine test assessment for measuring liver function in critically ill patients

Caffeine elimination was studied in 73 patients admitted to an intensive care unit, 33 of whom had liver disease. Mean plasma clearance of caffeine in patients with no liver disease (1.30 +/- 0.79 ml/kg/min) was significantly higher than in patients with liver disease (0.39 +/- 0.23 ml/kg/min). Mean half-life of caffeine in patients with liver disease (23.96 +/- 12.19 h) was significantly higher than in patients with no liver disease (7.25 +/- 3.04 h). No significant differences in distribution volumes were found. Receptor-operator curves (ROC) for plasma clearance and the half-life of elimination of caffeine showed a high diagnostic value. Therefore, the parameters for caffeine biotransformation, i.e. Cl and t1/2, are useful for assessing liver function in the population studied.

Pharmacokinetics of temafloxacin after multiple oral administration

Four multiple dose studies involving 102 healthy volunteers were reviewed to determine the sources of intersubject variability in the pharmacokinetics of temafloxacin. As a result of the preferential distribution of temafloxacin into muscle, liver and kidney compared with adipose tissue, the best anthropometric explanatory variable was found to be lean body mass, rather than total body mass or body surface area. Single dose studies have confirmed that the distribution volume of temafloxacin is smaller in subjects in whom the lean body mass:total body mass ratio is low, notably in females, the elderly, and those with hepatic impairment. Average creatinine clearance for the volunteers included in this analysis was normal (109 +/- 29 ml/min), and renal function was only a marginally significant covariate; however, renal clearance accounts for 60 to 70% of total clearance (CLT) and has been shown to be a major factor in the elderly, as well as in patients with renal or hepatic impairment. Since temafloxacin is partially reabsorbed renally, urine flow rate was found to be a potentially important secondary factor. Overall, the pharmacokinetics of temafloxacin are essentially linear, with steady-state plasma concentrations at trough (Cssmin) and 2h postdose (Css2h) averaging slightly more than 0.5 and 1.0 mg/L per 100mg administered every (q) 12h. For example, mean Cssmin and peak steady-state plasma concentration (Cssmax) values after administration of temafloxacin 600mg q12h were 3.3 +/- 1.1 and 6.2 +/- 1.8 mg/L, respectively. Total apparent clearance (CLT/F) and the terminal elimination half-life (t1/2) averaged 11 L/h (184 ml/min) per 55kg lean body mass and 8.4h, respectively. Considering that the data reviewed came from 4 studies with doses ranging from 100 to 800mg q12h, the intersubject coefficients of variation were low for an orally administered drug, ranging from 15.4% for t1/2, 20.6% for Css2h, 21.2% for CLT/F and 25% for Cssmin.